An energy-accumulating device using a transformer of this type is described in French patent application number 88 04672, filed Apr. 8, 1988. The hybrid impulse transformer therein is used for accumulating and storing energy by setting up a current in the inductance constituted by the primary winding, with the secondary winding being open circuit, and by maintaining this current loop in a circuit which is entirely superconducting, i.e. without loss. The energy is stored in the intense magnetic field generated in the transformer by the current. The coupling between the primary winding and the secondary winding enables said energy to be discharged in the form of a pulse in the secondary winding by interrupting the current in the primary after a utilization circuit has been connected to the secondary. The current pulse provided by the secondary winding is used, for example, to launch a projectile, e.g. in a so-called "electromagnetic" launcher.
In order to obtain high efficiency in energy storage, it is necessary for the coupling between the primary winding and the working magnetic field to be without loss. It is known that a toroidal transformer provides the best solution in this respect, particularly since the intensity of the magnetic field is such as to make it impossible to use a field-guiding magnetic circuit made of high permeability material since the material would saturate. In addition, the greater the coupling between the primary winding and the secondary winding, the lower the interrupting power required of the primary circuit. This requirement for close coupling thus assumes that the secondary winding is wound as close as possible to the primary winding.
The electrodynamic forces acting on the conductors of windings tend to increase the diameter of winding turns give rise to a centripetal resultant directed towards the axis of symmetry of the torus. Such a resultant must be withstood by a strength member for each of the windings.
For thermodynamic reasons, it is also desirable to place the secondary winding over the primary winding and not vice versa, with an electrical insulator and a thermal insulator being interposed between the windings.
It might be thought that a single strength member could be placed in the center of the torus, to support the above-mentioned centripetal resultants on both windings. However this is not possible because the resulting centripetal force acting on the primary winding would press the primary winding so hard against the secondary winding and the single strength member as to crush the thermally insulting material.
The object of the invention is thus to provide a toroidal hybrid impulse transformer provided with a strength member suitable for supporting the primary winding against the above-mentioned centripetal forces, while nevertheless allowing the secondary winding to be disposed as close as possible to the primary winding.